Bimetallic salts and derivatives thereof, their preparation and use in the complexing of ligands

ABSTRACT

Bimetallic salts, having the generic formula MM&#39;&#39;Xn wherein M is a Group IB metal, M&#39;&#39; is a Group IIIA metal, X is a halide and n is equal to the sum of the valences of M and M&#39;&#39;, are prepared by reacting the halogen salts of the individual metals, M and M&#39;&#39;, in a suitable solvent. The bimetallic salt formed thereby is a discrete monomeric species and can be utilized in the separation and recovery of various ligands, by preferential complexation. Complexation can be conducted with the bimetallic salt in the solid state, in solution, or as a slurry, and with the complexible ligand in the gaseous or liquid state. The ligand is recovered by decomplexation of the bimetallic salt-ligand complex or by displacement of the complexed ligand with another ligand.

UnitedStates Patent 91 Long et al.

[ June 3,1975

[ BIMETALLIC SALTS AND DERIVATIVES THEREOF, THEIR PREPARATION AND USE INTHE COMPLEXING OF LIGANDS [75] Inventors: Robert B. Long, AtlanticHighlands;

Fred A. Caruso, Elizabeth, both of NI; Richard J. DeFeo, Baton Rouge,La.; David G. Walker, Baytown, Tex.

[73] Assignee: Exxon Research and Engineering Company, Linden, NJ.

22 Filed: May 17,1971

21 Appl.No.: 144,302

Related US. Application Data [62] Division of Ser. No. 805,912, Sept. 3,1968, Pat. No.

OTHER PUBLICATIONS Chemical Abstracts, Vol. 60, 3008c, (1964). Turner eta1., J.A.C.S. Vol. 88, 1877, (1966).

Primary ExaminerH. Sneed Attorney, Agent, or Firm-M. Conner; F. Santoro[57] ABSTRACT Bimetallic salts, having the generic formula MM'X, whereinM is a Group IB metal, M is a Group IIlA metal, X is a halide and n isequal to the sum of the valences of M and M, are prepared by reactingthe halogen salts of the individual metals, M and M, in a suitablesolvent. The bimetallic salt formed thereby is a discrete monomericspecies and can be utilized in the separation and recovery of variousligands, by preferential Complexation. Complexation can be conductedwith the bimetallic salt in the solid state, in solution, or as aslurry, and with the complexible ligand in the gaseous or liquid state.The ligand is recovered by decomplexation of the bimetallic salt-ligandcomplex or by displacement of the complexed ligand with another ligand.

10 Claims, 1 Drawing Figure PATENTEDJEE" 3 EFFECT OF TEMPERATURE ONETHYLENE, PROPYLENE ETHYLENE AND CO-EQUILIBRIA WITH (TOLUENE)' 'CU AlC/4TEMPERATURE C 1 BIMETALLIC SALTS AND DERIVATIVES THEREOF, THEIRPREPARATION AND USE IN THE COMPLEXING OF LIGANDS This is a division ofapplication Ser. No. 805,912, filed Sept. 3, 1968 and now US. Pat. No.3,651,159.

FIELD OF THE INVENTION This invention relates to the preparation and useof novel monomeric bimetallic salts having the generic formula MM'Xwherein M is a Group IB metal, M is a Group IIIA metal, X is a halide,and n is equal to the sum of the valerices of M and M. Moreparticularly, this invention relates to the use of these novel salts inthe separation and recovery, by preferential complexation, of variousligands, i.e., electron donors. In another embodiment hereof, thisinvention relates to the preparation and use of novel complexes of thesebimetallic salts having the generic formula MMX L wherein M, M, X, and nare as described, L is a ligand, e.g., a hydrocarbon, and m is equal tothe complexing stoichiometry of R and is an integer from 1-4.

PRIOR ART 'The use of various salts as sorbents (complexing agents) forthe separation and recovery, i.e., purification, of various ligands iswell known to the art. Such salts as cuprous ammonium acetate andcuprous halides, e.g., cuprous chloride, have been widely employed torecover ligands such as acetylenes, butadiene, carbon monoxide,monoolefins, etc. While the use of such salts has generally beensuccessful, several disadvantages are associated with their use. Thus,the salts, particularly the cuprous ammonium acetate, do not have wideapplicability and have been useful in recovering only a few differentligands. The cuprous halides, although possessing the ability to recoverseveral types of ligands, necessitate the use of rather severeconditions. To illustrate, cuprous chloride has been found useful forcomplexing ethylene, e.g., as from ethane/ethylene streams. However,because the ethylene-cuprous chloride complex is relatively unstable,i.e., has a high dissociation pressure, at room temperature andatmospheric conditions, it is necessary to employ low temperaturesand/or high pressures to make ethylene recovery feasible. Thus, atatmospheric pressure, ethylene complexing starts at 169F. and at F. onlya 44 wt. percent recovery from 50 wt. percent ethylene streams can beobtained. Now, since commercial operations require better than a 90 wt.percent recovery, temperatures must bein the range of 35F. to 80F. withseveral hundred psi pressure to achieve such results. Obviously,compression and/or refrigeration costs greatly increase the cost ofproducing ethylene in this manner.

It has now been found, however, that ethylene recovery, for example, inexcess of 90 wt. percent, preferably in excess of 95 wt. percent, morepreferably in excess of 99 wt. percent, e.g., 99.9 wt. percent, can beachieved at room temperature and ambient pressures and that the purityof ethylene so recovered will be in excess of 99 wt. percent, when theinvention to be described herein is utilized. Moreover, this inventionprovides a sorbent that is more versatile than those previously in use,i.e., it is applicable to awide variety of ligands, has a greatercapacity for sorbing ligands, and

generally overcomes all of the shortcomings of prior art sorbents.

As used herein, the term ligand is defined as a complexible molecule,generally an unsaturated compound, capable of donating a pair ofelectrons and capable of forming a coordinating bond with a metal, M, asin 2(CH -CH-CH ).CuAlCl where the two propylene molecules arecoordinated to the copper atom. Also, the term complex as used herein ismeant to include adsorption as well as absorption and the product formedthereby, the process generally being referred to as sorption wherein asorbent (salt) sorbs (complexes) a sorbate (ligand) and the complex maythen be desorbed (decomplexed).

SUMMARY OF THE INVENTION In accordance with this invention, therefore,monomeric bimetallic salts having the formula MM'X, wherein M is a GroupIB metal, M is a Group IllA metal, X is a halide, and n is equal to thesum of the valences of M and M, are prepared by reacting the respectivehalides of M and M, the halide of M preferably being present in anexcess, in the presence of a suitable reaction medium, generally asolvent for the Group IIIA metal halide. The monomeric bimetallic saltcan then be easily recovered, e. g., by driving off the solvent and/orfiltering away excess Group [B salt, and utilized in the sorption ofvarious ligands, such as acetylene, monoolefins, polyolefins, conjugateddiolefins, aromatics, cyclic olefins, carbon monoxide, etc., andgenerally those compounds designated as ligands.

The bimetallic salts prepared in accordance herewith are discretemonomeric species and are to be distinguished from the crystalline,polymeric materials reported by Amma, JACS, 85, 4046 (1963), and Turnerand Amma, JACS, 88, 1877 (1966). These references report the formationof crystalline structures made up of infinite zigzagging sheets composedof tetrahedral Cu(I) and AlClf, the structure being reported in theformer article as:

C C1 C1 C1 e s I o 0 l o o o o a 0 CU A1 a n a Cu 0 n Cl C C1 C1 C1 0 Bo i o o a C1: A1 I C C6 C1 Cl C1. C1 C6115 o o I l o o 0 Q Q Q O C AL uo I v a a C1 C655 D O U Thus, the Cu(I) ion is bonded to Cl atoms ofthree different AlCl, tetrahedra and a benzene ring making the Cu(l) ionfour coordinate. The latter article further supports this structure andpresents X-ray data to prove that the complex forms pleated crystallinesheets with adjacent sheets being held together by van der Waals forces.

From an examination of the structure reported in the literature, it isreadily apparent that the benzene to Cu(l) mole ratio is 1:1 throughoutthe polymeric structure and the generic formula for such a polymer canbe written as (C H .CuAlCl wherein n represents a number much greaterthan one. It is believed that the crystalline polymer reported resultedfrom the manner in which it was prepared, i.e., in an evacuated systemusing dry benzene and anhydrous resublimed cuprous chloride andanhydrous resublimed aluminum chloride. Nevertheless, the procedureutilized herein, i.e., reacting halides of M and M in a suitable solventsuch as an aromatic, gives rise to a structure believed to be a discretemonomeric species which can be pictured as having the structuralformula:

/Cl /Cl 1. Cu l Cl Cl and its benzene derivative Cu \AF/ C H Cl Cl Fromformula II it is apparent that the benzene to Cu(l) mole ratio is 2:1and that the generic formula can be written as (C H .CuAlCl.,, which isstructurally far different from that reported by Amma. Moreover, anexamination of the two structures reveals that the Cu(l) of Amma isbonded to three separate Al through Cl bridges, whereas the structure offormula II shows the Cu(l) bonded to but one Al through only two Clbridges. Clearly, then, a different structure having rather differentproperties is reported herein, e.g., in the complexing of aromatics suchas benzene a 100 percent increase in stoichiometry over the Ammastructure can be obtained.

The difference in preparative technique which is believed to account forthe difference in structure and properties reported herein is believedto be due to the codissolving, with reaction, of the respective metalhalides in a stoichiometric amount of, for example, an aromatic such asbenzene, such that two moles of aromatic are present for each mole ofbimetallic salt (see formula II). A clear solution is obtained whichcontains no free, i.e., unbonded, aromatic, and which chemicallyanalyzes for (Aromatic) .MMX This structure is evidenced by dataobtained from chemical analysis of stoichiometry and nuclear magneticresonance (NMR) studies. Thus, after exchanging the aromatic complexwith propylene, NMR studies of a (Propylene) .CuAlCl sample showed thatthe Al was tetrahedrally bound to four Cl atoms and that two propylenemolecules were complexed.

The invention described herein has several distinct advantages overprior art complexing agents such as CuCl in that (a wide variety ofligands can be complexed at ambient conditions, due to the stabilizinginfluence of the Group IllA metal salt; (2) ligand to copper mole ratiosin excess of 1:1 can be achieved,

whereas CuCl could carry only one mole of monoolefin or one-half mole ofdiolefin per mole of copper; 5 and (3) aromatics can be complexedwhereas prior art compounds were capable of complexing only aliphatichydrocarbons.

The monomeric bimetallic salts have been described herein as having thegeneric formula MMX,,. Thus, M is a Group lB metal, i.e., copper,silver, or gold, copper (I) being particularly preferred. M is a GrouplllA metal, i.e., boron, aluminum, gallium, indium, thallium, whileboron and aluminum are preferred, aluminum being particularly preferred.X is a halide, i.e., fluoride, chloride, bromide, iodide, and chlorineand bromine are preferred, particularly chlorine. The most preferredbimetallic salts are CuAlCl, and CuAlBr particularly the chloridederivative, while other representative salts are CuBF CuBCl AgBF AgBClAgAlCl AgAlBr CuGaCl CulnCl CuThCl and the like.

The monomeric bimetallic salts of this invention are readily prepared byreacting the respective halides of M and M in a suitable reactionmedium. Since the bimetallic salt will generally be soluble, to someextent, in the same solvents as the Group lllA metal salt, it ispreferred to employ as a reaction medium, a solvent in which one of thesalts of either M or M is soluble or partially soluble and the other isinsoluble or relatively insoluble. Thus, Group lllA metal halides, suchas AlCl are generally soluble in aromatics, e.g., C -C aromatics,preferably C -C more preferably C5-C aromatics such as benzene, toluene,xylene, mesitylene, and most preferably toluene. On the other hand,Group 18 metal halides, such as CuCl, are soluble in C -C monoolefins,preferably C -C more preferably C -C monoolefins, e.g., ethylene,propylene, isobutylene, butenes, hexenes, heptenes, and the like, mostpreferably alpha monoolefins. Aromatic solvents, however, are motadvantageously utilized.

Of course, other components may also be present during the reaction solong as a solvent in which one salt is relatively soluble and the otheris relatively insoluble is present, and two such solvents may bepresent, e.g., reacting a solution of CuCl in a monoolefin and asolution of AlCl in an aromatic. Now, since the bimetallic salt willcomplex with a variety of compounds, including the such compounds, i.e.,ligands, as aromatics and monoolefins, a complex having the greateststability will form, and, in this instance, the monoolefin complex beingmore stable than an aromatic complex will form.

Other illustrative preparative techniques that may be employed involvecontacting solid CuCl with the aromatic solution of AlCl thereby forminga solution of CuAlCl .(Aromatic complex in the aromatic; contacting CuClslurried in a paraffin, e.g., a C -C paraffin, with an aromatic solutionof AlCl contacting solid AlCl or AlCl slurry with a solution of CuCl ina monoolefin, thereby forming a precipitate or solution of CuAlCl.(Monoolef1n) and any other combination that may be desirable under thecircumstances. Preferably, the solvent is employed in a stoichiometricrelationship to the bimetallic salt product. Thus, for aromatics andmonoolefins, such as ethylene or propylene, the stoichiometricrelationship can be one or two, preferably two, and, therefore, twomoles of solvent are then employed for each mole of cuprous chloride andaluminum chloride utilized.

The complex may then be recovered, e.g., by filtering, decanting, etc.the precipitated CuAlCl .(olefin) complex, or driving'off excess solventfrom CuAlCl .(Aromatic) and soluble CuAlCl .(Olefin complexes and thebimetallic salt obtained by decomplexing the complex, e.g., by heatand/or reduced pressure. A typical preparation technique is illustratedherein as (Ar Aromatic, S Solid, S1 Slurry, L Liquid):

blowing out any HCl or H 0 that may be present. Further, the halidesshould be stored in the absence of oxygen and water which tend tooxidize and hydrolyze the components, respectively. Similarly, thereaction to form the bimetallic salt and any reactions (sorbingprocesses) in which the bimetallic salt is employed should preferably berun under substantially anhydrous conditions and in the substantialabsence of oxygen. Generally, however, water and oxygen can be presentin amounts similar to that tolerated by Ziegler type cata- Theconditions under which the bimetallic salt is prepared are generally notcritical and may vary widely. It is only necessary that the system be inthe liquid state, i.e., the solvent is maintained in the liquid state,above the freezing point and below the boiling point of the particularsolvent utilized. Thus, temperatures under which the respective M and Mhalides can be contacted can range from about 40 to 300F. Thesetemperatures are practical limits since below about 40F. most of thepreferred aromatic solvents, or their complexes, tend to solidify whileabove about 300F. the most preferred C -C aromatics tend to boil, unlesspreparation is carried out above atmospheric pressure. Preferably,temperature range from about 0 to 150F. Pressures, too, may vary andsubatmospheric as well as superatmospheric pressures can be employed,for example, 0.1 to 1000 psi, preferably atmospheric to 100 psi.However, conditions of room temperature, i.e., l 8-25C. and atmosphericpressure can be advantageously employed.

One factor of considerable importance in the preparation of those novelsalts relates to the catalytic activity of free Group IIIA metal saltssuch as the highly active Friedel-Crafts catalyst AlCl In order toeliminate free AlCl for example, an excess of the Group B salt ispreferably employed, thereby insuring that all the AlCl reacts. It isonly necessary that some excess Group [B salt is present; however,preferably, the molar ratio of Group lB metal salt/Group lllA metal saltis at least 1.01 and more preferably ranges from about 1.02 to 1.2.Additional Group IB metal salt could be employed but this wouldgenerally lead to excess solids in the reaction medium, when an aromaticsolvent is employed, and these would only have to be removed, e.g., byfiltration. This procedure generally inhibits or neutralizes catalyticactivity of the sorbent for all but the most reactive of compounds,e.g., higher monoolefins of diolefins.

The starting materials utilized for the reaction should beof substantialpurity, e.g., 991 percent pure. Thus, recrystallized CuCl can beemployed and AlCl can be purified by heating while fluidizing withnitrogen and lysts, e.g., less than about 10 ppm water or oxygen.Additionally, the solvent selected for preparing the bimetallic saltshould not be capable of being polymerized by the Group IIIA metalhalide and only inert reaction media should be employed. Thus, aromaticsolvents are far more preferred than monoolefinic solvents.

The novel bimetallic salts or their derivatives, e.g., CuAlCl.(Aromatic) are quite useful in the sorption and separation andrecovery, in highly concentrated forms, of various ligands. The saltsare quite versatile and may be employed as solutions (in aromatics) oras liquid complexes of CuAlCl .(Aromatic) as a solid (fluidized or fixedbed), or as slurries (in paraffins with or without aromatic activators)and can be contacted with ligands wherein the ligand can be in eitherthe gaseous or liquid states. Thus, it is only necessary that the saltand the ligand be place in intimate contact and this is readily achievedby normal gas-solid, gas-liquid, liquid-solid, liquid-liquid contactingmeans. However, it is generally preferred to take advantage of thephysical state of the ligand in fixing the contacting means. Thus,

if the ligand is gaseous, the sorbent is generally liquid,

and, if the ligand is liquid, the sorbent may be liquid or solid. It isnoted generally that when the sorbent is employed as a solid, the ligandrecovery is increased as the temperature of the ligand approaches itsdew point, that is, a ligand should be within 30F. of its dew point,preferably within 20F., more preferably within 10F. of its dew point,with these temperatures above the dew point when utilizing a solidbimetallic sorbent.

A wide variety of ligands can be complexed, i.e., sorbed, by these novelbimetallic salts. Among these are unsaturated compounds such as olefins,acetylenes, aromatics, carbon monoxide, and the like. More specifically,the unsaturated hydrocarbons can be (a) acetylenes, such as C -Cacetylenes, preferably C -C acetylenes, e.g., acetylene, methylacetylene, ethyl acetylene, dimethyl acetylene, vinyl acetylene, etc.;(b) monoolefins, such as C -C monoolefins, preferably C -C morepreferably C -C monoolefins, most particularly ethylene and propylene;(c) conjugated diolefins, such as C -C conjugated diolefins preferably C-C conjugated diolefins, e.g., butadiene, isoprene, etc.; ((1)polyolefins, such as C -C preferably C -C polyolefins, e.g.,cyclododecatriene, cyclooctadiene; (e) cyclic olefins and alicyclicolefins, such as C -C preferably C -C e.g., cyclopentene, cyclohexene,cyclooctene, etc.; (f) aromatics, such as C -C aromatics, preferably C-C aromatics, e.g., benzene, xylene, toluene; and (g) cumulativediolefins, such as C -C cumulative diolefins, e.g., allene. The processis particularly applicable to sorbing C -C monoolefins, C -C acetylenes,carbon monoxide, and C -C aromatics. Any of the foregoing ligands can besorbed by the salt itself, while derivatives thereof, e.g., CuAlCl.(Aromatic) will sorb any ligand having a greater complex stability,i.e., an exchange reaction will occur, the more stable ligand displacingthe less stable ligand.

Generally, the compound to be sorbed, i.e., separated by preferentialcomplexation, and recovered is contained in a feed stream admixed withvarious other compounds which are either not sorbed or lesspreferentially sorbed, i.e., their complexes are less stable than thecomplex of the compound to be preferentially sorbed. For example, suchfeed streams as ethane/ethylene or propane/propylene (the paraffin notbeing sorbed) can be treated to concentrate the olefin. In cases,however, where several ligands can be sorbed, e.g., when a solid sorbentof slurry is employed, the complexed ligands can be decomplexed as awhole, or individually, and recovered by distillation or fractionaldecomplexing, respectively.

While the stability of various complexes will vary widely, it cangenerally be stated that monoolefin complexes are more stable thanacetylene complexes which, in turn, are more stable than carbon monoxidecomplexes which, in turn, are more stable than aromatic complexes. Inmonoolefin complexes, propylene complexes are more stable than ethylenecomplexes, and stability is believed to be related to molecular weight.Because of the wide range of ligands available for complexing, it isunderstood that several compounds of each class mentioned herein willoverlap compounds of other classes. Nevertheless, one skilled in the artcan readily determine, by routine experimentation, the exact order ofstability for any set of complexes.

The bimetallicsalt can be used as a dry solid, in a slurry with diluentssuch as C -C paraffms, C -C naphthenes, or as a solution in C -Caromatics or C C cycloolefins. Of course, when aromatic solutions areemployed, the aromatic complex is believed to form (and the sorbent isthen the aromatic complex rather than the salt alone), but since thearomatic complex is the least stable relative to the various othercomplexible ligands, the aromatic is readily displaced by the desiredligand, and the aromatic complex is a preferred sorbent because it is aliquid sorbent. Each of the sorbing techniques mentioned has advantagesand disadvantages regarding its use. For example, the complexing ofethylene with CuAlCL, as a dry solid or a paraffin slurry gives aninvariant equilibrium constant while the use of a toluene or otheraromatic solution or liquid aromatic complex of CuAlCL, gives a solutionequilibrium which depends upon the amount of reactants and productspresent. The invariant equilibrium has the advantage of permitting allof the CuAlCl, to be consumed in the process while the solution typeequilibrium limits conversion by the formation of free aromatic (bydisplacement) and the comsumption of the (Aromatic) .CuAlCl complex. Onthe other hand, product yield is limited by the dissociation pressure ofthe (Ethylene .CuAlCl complex in the invariant case whereas completeproduct recovery can be obtained in the solution case. It is generallypreferred, however, to employ aromatic solutions, i.e., liquid aromaticcomplexes, (because of their case in handling, e.g., heat ofcomplexation is readily dissipated both because it is balanced in ligandexchange and because of easier beat transfer,'intimate contact betweenligand and sorbent is promoted) of the bimetallic salt or paraffinslurries activated with at least about 10 mole percent, preferably about10 to about 300 mole aromatic, more preferably to mole percent aromaticbased on the bimetallic halide salt, the aromatics being thosepreviously described as useful for solution preparation. It is believedthat activation involves solution of the bimetallic salt by theactivator, e.g., C -C aromatics, and increasing amounts of activatorwill increase the solution of salt. Thus, the use of a slurry with anaromatic activator will approach, in operation and result, the use of anaromatic solution or liquid aromatic complex as the amount of activatorincreases.

It is interesting to note that the number of moles of ligand per mole ofcopper in the bimetallic salt increases from 1:1 to 2:1, for example, inmonoolefin complexes, as the system is changed from dry solid orparaffin slurry to aromatic solution or aromatic activated slurry and,therefore, the recovery of ligand is increased. This variable capacityof the salt with regard to ligands is an interesting phenomenonattendant to this invention. While the theoretical nature of thisphenomenon is not yet understood, it has been determined that thecomplexing stoichiometry, i.e., the number of moles of ligand that willcomplex with one mole of bimetallic salt varies, depending upon thereaction phase, e.g., liquid sorbent, solid sorbent, and the physicalstate of the ligand, e.g., liquid, gas. Thus, the generic formula of thecomplexes formed by ligands and the bimetallic salt may be representedas MMX L wherein M, M, X, and n have been previously described, L is acomplexible ligand as described, and m is equal to the complexingstoichiometry of the ligand and is an integer from 1 to 4. Now, sincethe ligands are coordinated to the M metal, e.g., Cu(I), and M has amaximum coordination number of 4, the maximum of m must be 4. The mostcommon form of coordination of M, however, ranges from 1 to 2 (an m of 2is shown above in formula 11). Generally, for aromatics and monoolefins,m is l to 2, usually 2; for example, i when only 1 mole of aromatic isused to form the complex; for carbon monoxide and acetylene, m isusually 1, and for cumulative olefins such as allene, m is usually 1.

While in many instances herein In is shown as 2, it is believed that asthe system becomes increasingly ionic, for as yet unknown reasons, oneof the bonds between Cu(I) and Cl is broken, thereby allowing anotherligand to complex with Cu(I), such as:

and in a completely ionic system where an [AlClflion and a [CuL4] ion ispresent, the structure would be:

L L c1 c1 lV. ilru Al L/ L Cl Cl which shows the breaking of both Cu(I)to Cl bonds. Again, while it is apparent that m may vary from 1 to 4,depending upon the nature of the systems, little is known about thetheoretical aspects of this variation. However, it is conceivable thatligand driving force may also play a role in the phenomenon and that thephysical state of the ligand and sorbent may affect that driving force.

It is also noted that in the generic formula MM'X,,L,,, L may be thesame or different. For example, an aromatic complex, such as (C l-I.CuAlCl4 can be treated with one mole of ethylene, which is a strongercomplexing agent than benzene, thusly:

(C ll )(C H .CuAlCl lC l-l (1) and treatment with another mole ofethylene yielding:

the overall equation being written as:

1 (C l-l .CuAlCl.,-l-2(C H Obviously, then a variety of complexes can beformed, depending upon the relative stability of ligands and treatmentratios. Additionally, the foregoing expressions also illustrate adisplacement reaction which can be utilized to recover ligands. As willbe discussed hereinbelow, these displacement reactions can be madereversible so as to aid in the recovery of a variety of ligands.

One of the particular advantages of this process is that ligandrecoveries can be obtained at reasonable conditions. Thus, whilesomewhat different conditions for complexing and decomplexing will applyfor different materials, conditions are generally not critical and mayvary widely. Thus, for any type of complexing, reaction temperatures mayrange from about -40F. to about 300F., preferably 40F. to 200F., andmore preferably about 50F. to 150F. Pressures similarly may vary widelyand can range from about 0.5 atmosphere to about 100 atmospheres,preferably 1 to 20 atmospheres. While decomplexing to recover a desiredligand may be carried out in a variety of ways, e.g., dissociation,displacement, decomplexing by dissociation will occur at a temperaturehigher than complexing (for constant pressure processes) and in therange of about 50F. to about 500F., preferably about 200F. to 400F., orat lower pressures than for complexing (for constant temperatureprocesses) and in the range of about 0.1 to 30 atmospheres, preferably0.5 to 20 atmospheres. Most preferably, however, liquid sorbent systemsare employed, and still more preferably liquid sorbent systems withgaseous ligands are employed. In these most preferred systems, the samegeneral conditions as already outlined will apply; however, liquidsystems are only limited by those conditions under which the ligandremains liquid.

Additionally, the complexed ligand can be used as a storage device forthat ligand. For example, in the case of carbon monoxide or other lowboiling ligands, storage is generally effected in pressure vessels as agas or in cryogenic containers as a liquid. In either case, ratherexpensive storage devices are required which are relatively hazardous,e.g., high pressures, or may result in large losses if a leak in aliquid system develops. Moreover, so long as the bimetallic salt isfully complexed, there is no danger of contamination in storage and anexceedingly high purity product can be stored and transported relativelyeasily. Further, higher molecular weight ligands, suchas aromatics, cannow be stored as solids at relatively high temperatures and also can bekept for long periods in an exceedingly high state of purity.

The recovery of the complexed ligand can be effected in a variety ofways depending upon the sorbent system that is employed. For example, ina solution system, using CuAlCl (Aromatic) for example, some monoolefincomplexes will precipitate, e.g., the ethylene complex, and can berecovered by filtration, decantation, centrifugation, etc: Filtration,etc. can also be employed to recover such complexes from slurry systems.After separation of the complex, it can be decomplexed by heating in thepresence of an inert stripping gas, e.g., nitrogen, helium, argon,carbon dioxide, and the ligand then is easily separated from thestripping gas, e.g., by condensation, distillation, etc., and the saltand slurry diluent are then recycled to the process. Obviously, thestripping gas could also be a boiling aromatic.

Another recovery method, which readily lends itself to continuousoperations involves reversible displacement reactions for solution typesorbent systems, i.e., use of aromatic solvents for bimetallic salt.Such displacement reactions may be readily exemplified by the followingexpressions which show the recovery of propylene using a toluenecomplex:

Complexing: (C H CH .CuAlCl +2(C H Displacement: (C H CH .CuAlcl +2(C H5 In equation (4) a liquid aromatic complex can be employed to recoverliquid or gaseous monoolefm from a feed stream containing propane andpropylene, for example. The resulting monoolefin complex is soluble inthe liquid medium formed by liberation of liquid toluene, gaseouspropane bubbling through unaffected since propane does not complex. Thepropylene can be recovered by heating to shift the equilibrium andstripping with inert gas or boiling toluene, equation (5), underconditions, i.e., higher temperature and/or lower pressure, which willfavor the reverse reaction. Thus, equations (4) and (5) may be writtenas a single reversible equation. The figure, attached hereto, is a logplot of equilibrium constant against temperature at constant atmosphericpressure of the reversible complexation of several ligands with a(Toluene) .CuAlCl., complex. In this plot, by operating at lowertemperatures, the products will increase, i.e., complexes of ethylene,propylene, or CO will tend to form at the expense of the toluenecomplex. The opposite is true for operation at higher temperatures.

As previously discussed, the use of an excess of Group 18 metal halideinsures the reaction of all of the Group IIIA metal halides and,therefore, substantially neutralizes the catalytic activity, e.g.,alkylation, polymerization, of the Group IIIA salts. Nevertheless, thebimetallic salt may contain some residual catalytic activity due to theacid nature imparted to it by the Group lIlA salt. This residualactivity generally will only appear when highly reactive ligands, e.g.,diolefins, such as butadiene, or C monoolefins such as hexene, heptene,etc., are utilized in the sorption process. Moreover, this catalyticactivity is further promoted when such reactive ligands are decomplexedby heating at high temperatures which can cause catalytic polymerizationor alkylation of the desired ligand. In such cases, it is advisable toemploy recovery methods such as displacement or decomplexation usingpressure changes rather than using increased temperatures fordecomplexation. Nevertheless, this residual catalytic activity (oracidity) can be effectively neutralized after preparation of thebimetallic salt by the use of certain additives, i.e., neutralizingagents. These neutralizing agents are generally characterized as basicmaterials, and are exemplified by ammonia and organic nitrogen baseswhich preferably have a boiling point in the same range as the reactionsolvent (if a solvent is employed) so as to insure the presence of theneutralizing agent under all reaction conditions. Examples of suchorganic nitrogen bases are aniline, pyridine, quinoline, trimethylamine,triethylamines, tri-n-butylamine, and the like, and C -C nitrogen basesgenerally. Additionally, Group VB metal trihalides can be effectivelyemployed as neutralizing agents, e.g., antimony trichloride, phosphoroustrichloride, arsenic trichloride, tribromide derivatives, etc. Undernormal circumstances, it is only necessary that small amounts ofneutralizing agent be present, e.g., merely enough to react with freeacidity of the system. In fact, the presence of too much neutralizingagent causes precipitation of copper salt from the solution leading toformation of a different catalytic species. Preferably, the neutralizingagent is present in an amount of at least about 0.01 wt. percent basedon sorbent, more preferably about 0.1 wt. percent. Preferred materialsare ammonia and pyridine which are preferably employed with aromaticsorbent solutions in amounts ranging from about 0.01-1 wt. percent basedon sorbent. (The neutralizing agents described herein can also beemployed in a like manner during the preparation of the bimetallic saltwhen C monoolefinic solvents are employed.)

Having now described the invention, the following examples will furtherserve to illustrate the preparation and use of these novel bimetallicsalts. However, no limitations are to be implied from these examplessince variations and modifications will be obvious to those skilled inthe art.

EXAMPLE 1 1.1 moles of carefully purified CuCl (109 grams) were mixedwith 1 mole of purified AlCl (133 grams) in an inert nitrogen atmosphereas dry powders. This powder was slowly added with agitation in an inertatmosphere to 2 moles 156 grams) of dry benzene. The mixture was allowedto stir for one hour. The clear, dark liquid was removed from the smallquantity of undissolved solids by decantation. The liquid was thentreated with anhydrous ethylene gas, and a solid ethylene complex wasformed. The solid was separated by filtration, and washed with pentanesaturated with ethylene. The solid was dried in a stream of ethylene.The dry solid was then heated in a vacuum, and the ethylene wasdecomplexed yielding the free CuAlCl Elemental analysis of the ethylenecomplex before decomposition showed:

Calculated: Cu 22.0 Al 9.4 Cl 49.1 C 16.7 H 2.8 Found: Cu 21.0 A] 9.7 CI53.2 C 17.1 H 3.1

This analysis corresponds to CuAlCl .2(C H and shows a 2:1 complex,indicating that the original benzene complex was a 2:1 complex.

EXAMPLE 2 Various ligands were recovered using a solution sorbent systemof CuAlCL, in toluene prepared by dissolving 232 grams of CuAlClprepared similarly as in Example 1 in 184 grams toluene. The ligand feedstreams were fed into solution as vapors by allowing the feed stream tobubble through the liquid and the complexed ligand recovered by heatingthe complex to the boiling point of the complex. Table I shows theresults of this experiment.

The results in this table clearly show the ability of the toluene.CuAlClcomplex to remove substantially completely the complexing ligand fromthe feed at room temperature and atmospheric conditions, and to producethe ligand upon decomplexing in exceedingly high purity.

ligand 3 The recovery of ethylene from an ethylene/ethane feed at roomtemperature and atmospheric pressure is shown in Table 11 using slurry,slurry-activated, and liquid aromatic complex sorbents.

TABLE II (Slurry) 34 Wt.% CuAlCl,

(Slurry-Activated) 29 Wt CuAlCl, 55 Wt.% CuAlCL,

capacity of the sorbent for ethylene.

EXAMPLE 7 The use of a Slurry of CuAlCl to Complex Ethylene from anEthylene-Ethane Mixture A slurry of CuAlCl, in heptane was prepared asfollows: The CuAlCl .benzene complex was prepared by dissolving 109grams (1.1 moles) of pure CuCl and 133 grams (1 mole) or pure AlCl in 2moles of benzene.

EXAMPLE 4 The clear solution was then treated with pure ethylene TableIII shows the recovery of various ligands with to Complex 2 moles ofethylene P mole of 4- a complex ligand sorbent system f C A1C1 Thissolid complex was separated from the benzene, (to1uene)2 washed withpentane, which was saturated with ethyl- I TABLE III Feed C /C /C-fCO/CH4/H2 2 .l 2

Complexed Ligands C2/C3 CO 2 :l Temp., C. 24 25 27 Pressure, Psig 0Ligand Content, Mole 1 Feed 32.5 C;-/35.6 C," 32.1 14.5 C. ."/19.0 C,"Initial Tail as 3.4 C2/5.5 C{ 5.0 3.2 C{ /l.4 Q, Decomplexed 65.2C2/34.8 C2 100.0 34.1 C2/65.9 C3 Product (100) (100) (100) EXAMPLE 5ene, and was dried in a stream of pure ethylene. The

CuAlCl .(C-,H,.) Calculated: C 40.3 A1 6.5 H 3.9 CI 34.1 Cu 15.2 Found:C 39.4 A1 6.4 H 4.1 CI 34.4 Cu 14.4

Portions of this solution were treated with a synthetic feed containingpercent propane and 50 percent propylene. One portion was treated as is,and a second was treated after addition of 0.1 percent anhydrousammonia. In the case of the ammonia treated sorbent,

propylene was complexed without side reactions. In the 50 case of theuntreated sorbent, side reactions accounting for over 10 percent of thepropylene were obtained. Gas chromatographic analysis of the liquidshowed the presence of alkylated aromatics and oligomers of propylene.

EXAMPLE 6 A CuAlBr .(Benzene) complex was prepared by a procedureanalogous to that for CuAlCl .(Toluene) This solution, clear green incolor, was used to separate carbon monoxide from a feed mixturecontaining 21% CO, 74% H and 5% CH Complexation was carried out at 800psig and 25C. The carbon monoxide was complexed selectively. At the endof the feed addition,

the reactor was depressured to O psig, and the complex 5 was decomposedat 60C. to yield carbon monoxide of 99.5% purity.

ethylene was removed from the complex by heating under vacuum, leavingpure CuAlCl The solid was 0 suspended in pure, dry, normal heptane suchthat a 50 percent by weight slurry was obtained. Benzene, 0.1 mole, wasadded as an activator.

The slurry was stirred in a well agitated reactor, and a feed streamcontaining 50 percent ethylene and 50 percent ethane was passed throughthe slurry. The ethylene was absorbed until a complex was obtained whichcorresponded to 2 moles of ethylene per mole of bimetallic salt.(Complexation was carried out at ambient temperature and atmosphericpressure.)

The slurry was then heated to the boiling point of the heptane diluentand the complexed ethylene was evolved in better than 99 percent purity.The heptane diluent was stripped from the gas by an efficient condenser.The decomplexed slurry was then capable of being returned to thecomplexer for another cycle.

EXAMPLE 8 Nuclear Magnetic Resonance Studies A study was carried out ofthe exchange of a toluene complex of CuAlCl to a propylene complex. 2Propylenes CuAlCl .(Toluene)?CuAlCl .(Propylene) Toluenes.

Samples were prepared in a dry box which represented the initial tolueneCuAlCl, complex and 25, 50, 75, and 100 percent exchange with propylene.These samples were sealed in NMR tubes, and subjected to Proton NMR. Theresults are summarized as follows:

1. Propylene is present in increasing amount as the exchange takesplace. The propylene spectra are shifted from that of pure propylene andindicate the donation of electrons.

2. The initial toluene spectra are shifted from that of free toluene andgive only a single sharp peak. As the exchange takes place, this peakchanges and shifts to that of free toluene so that no complexed tolueneappears present at the end of the exchange.

3. The exchange data confirm that two moles of ligand are exchangedduring the experiment.

EXAMPLE 9 Allene Stoichiometry A solution of CuAlCl .(Toluene) in excesstoluene which contained 3.09 moles per liter of copper was used toabsorb allene from a 50:50 allene-propane mixture at room temperatureand atmospheric pressure. The amount of allene absorbed was calculatedfrom analysis of the gas leaving the absorber and measurement of itsvolume. A total of 2.62 moles per liter of allene was absorbedcorresponding to a ratio of 2.62:3.09 or 0.85 mole of allene per mole ofCu. This indicates an allene/Cu mole ratio of 1.0.

EXAMPLE 10 Ligand Exchage Rapid ligand exchange has been demonstratedfor a variety of pairs of complexing ligands. In these experiments the(Toluene) .CuAlCl complex was treated at room temperature in a gasbubbler with a gas containing another ligand (either ethylene, CO, oracetylene) until the Cu would no longer pick up any of the gaseousligand. Then a second gas containing a different complexing ligand wasused to strip the solution and the exit gas was analyzed by gaschromatography. Finally, when no further changes in compositionoccurred, the solution was heated to 140C. to liberate whatever wascomplexed on the CuAlCl This gas was also analyzed by gaschromatography. The results are shown in the following table.

purify both Co and ethylene from their mixtures with non-complexinggases. Absorption was carried out at room temperature and atmosphericpressure while regeneration of the solution was carried out at 100C.using nitrogen stripping gas.

TABLE V Feed Gas 50/50 COl-l 50/50 Ethylene Ethane Ligand Complexed COEthylene Initial Tail Gas, Ligand 3.0 1.5

Moles Ligand/Mole Cu 1 l Purity of Decomplexed Product, Ligand 999* 99.9

These data show that the bromine analog of CuAlCL, works about the sameas the chlorine compound and can be readily prepared in aromaticsolvents. Furthermore, it exchanges readily with other ligands.

TABLE IV First Complexing Ligand Ethylene CO Acetylene Stripping GasPropylene Ethylene Ethylene First Exit Stripping Gas 86.7% C 90.1% C0 2%C Last Exit Stripping Gas 99.94% C," 100% C; 99.06% C{ DecomplexedProduct 99.97% C 99.94% C 8,

the original ligand obtained upon decomplexing shows that it wasessentially completely removed by stripping with the second ligand.

EXAMPLE 1 l Complexing with CuAlBr A toluene complex of CuAlBr wasprepared by slurrying together solid CuBr and solid AlBr in toluene atroom temperature. The liquid (Toluene) .CuA1Cl complex formed readilyand was used to recover and 4. The salt of claim 3 wherein L is a C -Cmonoole fin and m is 2.

5. The salt of claim 3 wherein L is ethylene and m is 2.

6. The salt of claim 3 wherein L is propylene and m is 2.

7. The complex composition having the genenric formula CuAlCl .L whereinL is a complexible ligand C C mono-olefins and m is equal to thecomplexing stoichiometry of L and ranges from 1 to 4.

8. The complex composition of claim 7 wherein L is a C -C mono-olefinand m is 2.

9. The complex composition of claim 7 wherein L is ethylene and m is 2.

10. The complex composition of claim 7 wherein L is propylene and m is2.

1. A COMPLEX BIMETALLIC SALT HAVING THE GENERIC FORMULA CUALX4LM WHEREINX IS SELECTED FROM THE GROUP CONSISTING OF CHLORINE, BROMINE ANDFLOURINE ATOMS, L IS A COMPLEXIBLE LIGAND (, SAID LIGAND SELECTED FROMTHE GROUP CONSISTING OF CARBON MONOXIDE, C2-C6 ACETYLENES,) C2-C20MONO-OLEFINS (,C4-C10 CONJUGATED DIOLEFINS, C6-C16 POLYOLEFINS, C5-C10CYCLIC OLEFINS AND C3-6 DIOLEFINS) AND M IS EQUAL TO THE COMPLEXINGSTOICHIOMETRY OF L AND IS AN INTEGER RANGING FROM 1 TO
 4. 1. A complexbimetallic salt having the generic formula CuAlX4Lm wherein X isselected from the group consisting of chlorine, bromine and flourineatoms, L is a complexible ligand (, said ligand selected from the groupconsisting of carbon monoxide, C2-C6 acetylenes,) C2-C20 mono-olefins(,C4-C10 conjugated diolefins, C6-C16 polyolefins, C5-C10 cyclic olefinsand C3-C6 diolefins) and m is equal to the complexing stoichiometry of Land is an integer ranging from 1 to
 4. 2. The salt of claim 1, wherein Lis selected from the group consisting of (C2-C4 acetylenes,) C2-C10mono-olefins (, and C4-C6 conjugated diolefins).
 3. The salt of claim 1wherein X is chlorine or bromine.
 4. The salt of claim 3 wherein L is aC2-C10 monoolefin and m is
 2. 5. The salt of claim 3 wherein L isethylene and m is
 2. 6. The salt of claim 3 wherein L is propylene and mis
 2. 7. The complex composition having the genenric formula CuAlCl4.Lmwherein L is a complexible ligand C2-C10 mono-olefins and m is equal tothe complexing stoichiometry of L and ranges from 1 to
 4. 8. The complexcomposition of claim 7 wherein L is a C2-C10 mono-olefin and m is
 2. 9.The complex composition of claim 7 wherein L is ethylene and m is 2.